JPH11281961A - Driving method for color liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an off icon from being seen as a void even at a low temperature in a color liquid crystal display element utilizing retardation. SOLUTION: In this method, the color liquid crystal display element is driven which includes a dot matrix display part 30 and an icon display part 20 in a display area and varies a driving voltage applied between transparent electrodes to control the color tone in the display area and utilizes retardation. In this case, The dot matrix display part 30 is driven by a time division driving system, and the icon display part 20 is driven by a static driving system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a retardation (R)
More specifically, the present invention relates to a method for driving a color liquid crystal display element in which an icon display section and a dot matrix display section are provided in a display area.

[0002]

2. Description of the Related Art First, the structure of a color liquid crystal display device using retardation will be schematically described with reference to FIG. In this color liquid crystal display device, the liquid crystal panel 1
Is provided with two transparent substrates 1B, 1B bonded in parallel to each other via a sealing material 1A. Although not shown, a transparent electrode and an alignment film are formed on each of the opposing surfaces of the transparent substrates 1B and 1B.

A nematic liquid crystal 1C containing a rotatory substance and having a positive dielectric anisotropy is sealed in a cell between the transparent substrates 1B, 1B. In this case, the twist angle of the liquid crystal molecules is determined by the alignment film. 160-300 degrees. The product (Δn1 × d1) of the refractive index anisotropy (Δn1) of the liquid crystal layer and the thickness (d1) of the liquid crystal layer is, for example, 1.2 at 25 ° C.
２．５2.5 μm.

On both surfaces of the liquid crystal panel 1, polarizing plates 2 and 3 are disposed, respectively, and a phase difference plate 4 is disposed between the front polarizing plate 2 and the liquid crystal panel 1. Further, a reflection plate 5 is arranged on the lower surface of the rear polarizing plate 3.

In this color liquid crystal display element, a color display is realized by controlling the voltage applied to the transparent electrode to change the retardation of the liquid crystal.
Therefore, it is possible to provide an inexpensive and bright color display without requiring a color filter, and to provide a low power consumption type color liquid crystal display element which does not require a backlight.

Therefore, this color liquid crystal display element is particularly suitable for a display panel of a portable information terminal device or the like, and FIG. 4 shows a liquid crystal display panel 10 applied to a portable telephone as an example. .

According to this, the liquid crystal display panel 10 is provided with an icon (icon) display section 20 and a dot matrix display section 30. Icon display section 2
Reference numeral 0 denotes a so-called pictograph display unit. In this example of the mobile phone, the icon display unit 20 has a reception sensitivity display unit 21 for displaying the reception sensitivity of the antenna, and a battery capacity display unit 22 for displaying the remaining capacity of the internal battery. Are provided.

The dot matrix display section 30 has an X electrode group 31 as a scanning electrode and a Y electrode group 32 as a signal electrode.
By applying a drive voltage to any of these intersections, abbreviated telephone numbers, transmission dial numbers,
In addition, information (data) such as message information is displayed.

In this conventional example, the icon display unit 2
0 is also incorporated as one line of the dot matrix, and is driven in a time-sharing manner together with the dot matrix display section 30.

That is, the icon display section 20 is composed of a so-called solid pattern 201 and pictogram patterns 202 opposed to the so-called solid pattern.
Numeral 1 is formed on one transparent substrate 1B side together with the X electrode group 31, and the extraction electrode serves as a scanning electrode.
Added to one of the

On the other hand, each pictogram pattern 202 is formed on the other transparent substrate 1B side together with the Y electrode group 32, and each extraction electrode is extracted through the space between the Y electrodes, and is inserted into the Y electrode group 32 as a signal electrode. Added.

Time-division driving (cumulative response type matrix driving)
In the method, the scanning time of one line is set shorter than the response time of the liquid crystal, and after repeating the scanning of the entire screen several times, the transmittance of the liquid crystal reaches a steady state (transmitted or non-transmitted) ( So-called voltage averaging method).

The graph of FIG. 5 shows the relationship between the effective value (Von or Voff) of the driving voltage waveform and the transmittance. In a liquid crystal display panel using this retardation, white is generated at Voff (off voltage). , Von (ON voltage), and blue at an intermediate voltage.

[0014]

As shown in the graph of FIG. 5, at normal temperature (25 ° C.), the non-voltage application section (the icon display section 20 and the dot matrix display section 30 of the liquid crystal display panel 10). (The background portion excluding) is almost white, so that the pictogram pattern 202 set to the Voff voltage in the icon display section 20 has the same color as the background and cannot be seen.

However, since the liquid crystal display panel using retardation has a high (Δn1 × d1), at a low temperature (for example, 0 ° C. or lower), the non-voltage applying portion turns dark green (see a chain line in FIG. 5).

On the other hand, according to the time division driving method,
As described above, since the pictogram pattern 202 (off icon) which is set to the Voff voltage because it is not turned on is white, the off icon becomes white as shown in FIG. 6 and may be mistaken for lighting. Was. In FIG. 6, the pictogram pattern 202 with hatching is in a lighting state.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a color liquid crystal display device using retardation so that an off icon does not appear as a white spot even at a low temperature. It is another object of the present invention to provide a driving method.

[0018]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a transparent electrode and an alignment film formed on the transparent electrode, each of which is disposed substantially in parallel with each other.
A nematic liquid crystal containing an optical rotatory substance and having a positive dielectric anisotropy is sandwiched between two transparent substrates, and the twist angle of the liquid crystal according to the alignment direction of the liquid crystal molecules formed by the alignment film of each transparent substrate is 160 to 300. And the product of the refractive index anisotropy (Δn1) of the liquid crystal layer and the thickness (d1) of the liquid crystal layer (Δn1 ×
d1) is set to a predetermined value, and at least one polarizing plate and one retardation plate are provided outside the liquid crystal layer, and a dot matrix display section and an icon display section are provided in a display area formed by the transparent electrode. The method for driving a color liquid crystal display element using the retardation of the liquid crystal and the retardation plate, wherein the method includes controlling a color tone in the display area by changing a driving voltage applied between the transparent electrodes. The matrix display section is driven by a time-division driving method, and the icon display section is driven by a static driving method.

Since the static driving method is a method in which a voltage is applied to each display pixel independently, the voltage applied to the off pixels is 0 V, which is the same as the background portion. Therefore, at a low temperature of 0 ° C. or lower, the off-pixel portion also exhibits the same dark green color as the background portion, so that the color is not removed.

[0020]

Next, an embodiment of the present invention will be described with reference to FIG. This embodiment also relates to a liquid crystal display panel for a cellular phone similar to that described above with reference to FIG. 4, and the same or similar portions are denoted by the same reference numerals as in FIG. .

The liquid crystal display panel 10A is provided with an icon display section 20 as a pictograph display section and a dot matrix display section 30 as an information display section, but their driving circuits are separate.

That is, the X electrode group (scanning electrode) 31 and the Y electrode group (signal electrode) 32 of the dot matrix display section 30
Are connected to a time-division driving circuit 41, and are subjected to time-division driving (cumulative response matrix driving) by the voltage averaging method described above.

On the other hand, the icon display section 20 is connected to a static drive circuit 42. In this case, the solid pattern 201 formed on one transparent substrate 1B (see FIG. 3) is connected to the common terminal of the static drive circuit 42, and each pictogram pattern 202 formed on the other transparent substrate 1B is statically driven. It is connected to the segment terminal of the circuit 42.

A predetermined voltage is applied to the solid pattern 201 from the common terminal of the static drive circuit 42, and a predetermined voltage is applied to the pictogram pattern 202 to be turned on independently from the segment terminals of the static drive circuit 42. . The applied voltage is appropriately selected according to the color to be displayed as shown in the graph of FIG. 5, and the gradation control is performed by PWM (pulse width).
(modulation) method.

In this way, the desired pictogram pattern 202 is displayed in color. The drive voltage of the non-lighted pictogram pattern 202 is set to 0V. That is, in the static drive method, the off-voltage is 0 V, whereby the unlit pictogram pattern 202 has the same color as the background portion (non-voltage applied portion).

For example, at a low temperature of 0 ° C. or less, the background portion is dark green, but the unlit pictogram pattern 202 is also dark green, as shown in FIG.
No white spots occur.

On the other hand, when the ambient temperature is, for example, 25 ° C., as can be seen from the graph of FIG. 5, the background portion and the unlit pictogram pattern 202 are almost white. As shown in the figure, the unlit pictogram pattern 202 is buried in the background and cannot be seen. In FIG. 2, the pictogram pattern 202 with hatching is in a lighting state.

In FIG. 1, for convenience of drawing, the lead lines of each pictogram pattern 202 and the lead lines of the Y electrode group 32 are set in different directions from each other. May be mixed in the Y electrode group 32 and drawn in the same direction together with the lead lines of the Y electrode group 32.

[0029]

As described above, according to the present invention,
In the color liquid crystal display element using the retardation, the icon display section is driven by the static driving method separately from the dot matrix display section, so that the white spot phenomenon of the pictogram pattern especially at low temperatures can be eliminated.

In addition, since the icon display section is driven by the static driving method, the power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing one embodiment of a liquid crystal display panel according to the present invention.

FIG. 2 is an explanatory diagram for explaining a white spot prevention effect of the embodiment.

FIG. 3 is a schematic cross-sectional view illustrating a configuration of a color liquid crystal display element using retardation.

FIG. 4 is a schematic plan view showing a liquid crystal display panel as a conventional example.

FIG. 5 is a graph showing a relationship between a driving voltage of a color liquid crystal display element using retardation and a liquid crystal transmittance.

FIG. 6 is an explanatory diagram for explaining a white spot phenomenon occurring in the conventional example.

[Explanation of symbols]

 10A Liquid crystal display panel 20 Icon display section 201 Solid pattern 202 Pictogram pattern 30 Dot matrix display section 31 X electrode group (scanning electrode) 32 Y electrode group (signal electrode) 41 Time division drive circuit 42 Static drive circuit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G09G 3/20 620 G09G 3/20 620A 621 621K 3/36 3/36

Claims (1)

[Claims] 1. A semiconductor device comprising: a transparent electrode; and an alignment film formed on the transparent electrode.
A nematic liquid crystal containing an optical rotatory substance and having a positive dielectric anisotropy is sandwiched between two transparent substrates, and the twist angle of the liquid crystal according to the alignment direction of the liquid crystal molecules formed by the alignment film of each transparent substrate is 160 to 300. And the product of the refractive index anisotropy (Δn1) of the liquid crystal layer and the thickness (d1) of the liquid crystal layer (Δn1 ×
d1) is set to a predetermined value, and at least one polarizing plate and one retardation plate are provided outside the liquid crystal layer, and a dot matrix display section and an icon display section are provided in a display area formed by the transparent electrode. A method for driving a color liquid crystal display element using the retardation of the liquid crystal and the retardation plate, wherein the method includes controlling the color tone in the display area by changing a driving voltage applied between the transparent electrodes. A method for driving a color liquid crystal display element, wherein a matrix display section is driven by a time-division driving method, and the icon display section is driven by a static driving method.